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UNS N08800 Allen Head Bolt
QS Fastener: UNS N08800 Allen Head Bolt
Name: UNS N08800 Allen Head Bolt
Material: Incoloy 800
Length: 150 mm
Size: 1 inch
Hardness: 170 to 220 HB
Application: For Heat Exchangers and Piping Systems
Feature: High Temperature Corrosion Resistance
Material: Incoloy 800
Length: 150 mm
Size: 1 inch
Hardness: 170 to 220 HB
Application: For Heat Exchangers and Piping Systems
Feature: High Temperature Corrosion Resistance
Quantity
The UNS N08800 Allen Head Bolt is manufactured from Incoloy 800 (1"×150mm), a high-performance heat-resistant alloy with a hardness range of 170-220 HB. Designed for high-temperature corrosive environments, it offers exceptional oxidation and carburization resistance, making it the ideal fastener for heat exchangers, piping systems, and other high-temperature, high-pressure applications. Its reliability ensures long-term stability in harsh operating conditions, widely used in petrochemical, power generation, and chemical industries.
1. High-Temperature Oxidation Resistance & Engineering Validation
The UNS N08800 Allen Head Bolt demonstrates superior long-term oxidation resistance up to 1100°C, attributed to a dual-protection mechanism:
The UNS N08800 Allen Head Bolt demonstrates superior long-term oxidation resistance up to 1100°C, attributed to a dual-protection mechanism:
1.1 Cr₂O₃ Oxide Layer Protection
- Above 600°C, the UNS N08800 Allen Head Bolt forms a continuous, dense Cr₂O₃ layer (1-3μm), governed by parabolic growth kinetics (diffusion-controlled). Test data confirms:
- 800°C/1000h: Oxidation weight gain ≤1.5 mg/cm² (ASTM G54 test).
- 1100°C/100h: Oxide layer remains intact (SEM confirms no spalling).
- Compared to 304 stainless steel (where Cr₂O₃ evaporates above 900°C), the high nickel content (30-35%) in UNS N08800 Allen Head Bolt significantly suppresses CrO₃ gas-phase volatilization, extending service life.
- Above 600°C, the UNS N08800 Allen Head Bolt forms a continuous, dense Cr₂O₃ layer (1-3μm), governed by parabolic growth kinetics (diffusion-controlled). Test data confirms:
- 800°C/1000h: Oxidation weight gain ≤1.5 mg/cm² (ASTM G54 test).
- 1100°C/100h: Oxide layer remains intact (SEM confirms no spalling).
- Compared to 304 stainless steel (where Cr₂O₃ evaporates above 900°C), the high nickel content (30-35%) in UNS N08800 Allen Head Bolt significantly suppresses CrO₃ gas-phase volatilization, extending service life.
1.2 Ti/Al Synergistic Strengthening Effect
- Titanium (0.15-0.60%) and Aluminum (0.15-0.60%) in the alloy form TiO₂ and Al₂O₃ dispersions at high temperatures, filling grain boundary defects in the Cr₂O₃ layer (verified by EDS analysis). This reduces oxidation rates by 30-40%.
- Titanium (0.15-0.60%) and Aluminum (0.15-0.60%) in the alloy form TiO₂ and Al₂O₃ dispersions at high temperatures, filling grain boundary defects in the Cr₂O₃ layer (verified by EDS analysis). This reduces oxidation rates by 30-40%.
Industrial Case Study: An ethylene cracking furnace using UNS N08800 Allen Head Bolt (M24×120) showed after 18 months at 950°C:
- No oxide scale buildup on threaded surfaces.
- Torque retention >85%.
- No oxide scale buildup on threaded surfaces.
- Torque retention >85%.
2. Carburization Resistance: Metallurgical Principles & Test Data
In carbon-rich environments (>800°C), such as carburizing furnaces and reforming units, the UNS N08800 Allen Head Bolt outperforms conventional austenitic stainless steels due to:
In carbon-rich environments (>800°C), such as carburizing furnaces and reforming units, the UNS N08800 Allen Head Bolt outperforms conventional austenitic stainless steels due to:
2.1 Carbon Diffusion Suppression
- High nickel content (30-35%) drastically reduces carbon solubility in the γ-austenite matrix (only 0.02 wt% at 800°C—1/5 that of 316 stainless steel).
- Ti and Al preferentially react with free carbon to form TiC and Al₄C₃, preventing deep carbon penetration (carburization depth <50μm @800°C/2000h).
- High nickel content (30-35%) drastically reduces carbon solubility in the γ-austenite matrix (only 0.02 wt% at 800°C—1/5 that of 316 stainless steel).
- Ti and Al preferentially react with free carbon to form TiC and Al₄C₃, preventing deep carbon penetration (carburization depth <50μm @800°C/2000h).
2.2 Surface Reaction Barrier
- In CO/CH₄ atmospheres, the UNS N08800 Allen Head Bolt develops a nanoscale Cr₃C₂-TiC composite layer (XRD-verified), with thermodynamic stability two orders of magnitude higher than Fe₃C (ΔGf₈₀₀°C = -45 kJ/mol).
- In CO/CH₄ atmospheres, the UNS N08800 Allen Head Bolt develops a nanoscale Cr₃C₂-TiC composite layer (XRD-verified), with thermodynamic stability two orders of magnitude higher than Fe₃C (ΔGf₈₀₀°C = -45 kJ/mol).
Comparative Test (ASTM G79):
| Condition | UNS N08800 Allen Head Bolt | 310S Stainless Steel |
| 850°C/CH₄ Atmosphere | 0.1mm/year carburization | 0.8mm/year |
| Surface Hardness Change | +20 HV | +150 HV |
Preventive Recommendation:
- For extreme carburizing environments (>900°C), pre-oxidation treatment (900°C/2h, air atmosphere) can be applied to pre-form a Cr₂O₃ layer, reducing carburization risk by >50%.
- For extreme carburizing environments (>900°C), pre-oxidation treatment (900°C/2h, air atmosphere) can be applied to pre-form a Cr₂O₃ layer, reducing carburization risk by >50%.
3. Industry Applications & Material Comparison
The **UNS N08800 Allen Head Bolt** excels in:
- Petrochemical: High-temperature fastening in ethylene crackers, catalytic reformers.
- Power Generation: Critical connections in gas turbines, boiler systems.
- Chemical Processing: Resistance to acidic/alkaline gas corrosion, prolonging equipment lifespan.
The **UNS N08800 Allen Head Bolt** excels in:
- Petrochemical: High-temperature fastening in ethylene crackers, catalytic reformers.
- Power Generation: Critical connections in gas turbines, boiler systems.
- Chemical Processing: Resistance to acidic/alkaline gas corrosion, prolonging equipment lifespan.
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